This invention relates to the field of food products and oil stabilizing components thereof.
The description below is provided solely to assist the understanding of the reader, and is not an admission that any of the information constitutes prior art to the present invention.
Peanut butter is a food paste prepared by grinding shelled, roasted, skinned and degermed peanuts. It is used directly as a paste, or as an ingredient in many food products, including sandwich and cracker spreads, candies and desserts, cooking sauces, and baked products.
In the United States, to be packaged and labeled as peanut butter, the paste must contain a minimum of 90% by weight peanuts. The remaining 10% may include optional ingredients such as sugar, salt, preservatives, stabilizers, non-peanut fats, modified fats, and fat substitutes. Approximately 50% by weight of the peanut butter is fat.
The term "natural" peanut butter generally refers to a peanut butter whose fat (triglyceride) content is limited to natural (unmodified) peanut oil. A two tablespoon (32 g) serving of such peanut butter having a fat content of 50% by weight, contains approximately 16 g of peanut oil. When a peanut butter is reduced in its fat content by at least 25% (to approximately 12 g per serving), the product qualifies as a "reduced fat" product in the U.S.
In other countries, peanut butter is defined by different standards. For example, in Malaysia peanut butter must contain at least 85% by weight peanuts, of which at least 20% must be protein. Edible fat and oil content may be not more than 55% and water content not more than 3%, with optional salt and hydrogenated vegetable oil being not more than 2% and 5% respectively (Laws of Malaysia, 1985 Malaysia Food Regulations, Article R.259).
Notwithstanding these definitions, for the purposes of the present invention, peanut butter is defined as any food product (including butters, spreads, pastes, sauces, toppings and the like), the majority of which (at least 50% by weight) is ground peanuts.
In the process of grinding peanuts to make fine, coarse, and chunky styles of peanut butter, a substantial amount of free peanut oil is released, producing a viscous suspension of solid peanut particles in oil. During storage of the peanut butter at room temperature, the peanut oil separates from the peanut solids, and when packaged in a container, the peanut solids settle to the bottom, and an oil layer forms at the surface. Following purchase of currently available natural peanut butters, the separated peanut oil supernatant phase is generally hand-mixed with the underlying solids within the container. This mixing tends to be awkward and is apt to result in oil spillage, but is important in providing an easily spreadable peanut butter product which, in the U.S., is often spread on slices of soft bread to make the traditional peanut butter and jelly sandwich.
Refrigeration of natural peanut butter significantly retards oil separation, but also significantly thickens the product, impairing ones ability to spread the peanut butter, particularly on soft bread. Without refrigeration, and depending upon the ambient temperature, oil separation can become an annoyance within a short time, e.g., a week or two. Removal of the major proportion of free peanut oil is not a satisfactory solution to the problem of oil separation because the remaining solids form a relatively dry paste which is difficult to spread. Accordingly, manufacturers of commercial peanut butter remove only approximately 25% of the peanut oil to produce a "reduced fat" product, and a fat substitute such as maltodextrin (which is also considered a bulking agent) is often added to replace the fat removed, to improve the fluidity and spreadability of the product.
The current commercial method used for eliminating oil separation in peanut butter is to supplement the peanut butter with a suitable stabilizer such as a fat which is solid at room temperature (e.g., partially and/or fully hydrogenated vegetable oil) which binds together the peanut solids and oil by forming a semi-solid matrix or paste. An Eastman Chemical Company brochure entitled "Stabilizers for Peanut Butter" (Publication ZM-91A, November 1993) states,
Stabilizers help provide good spreadability over a wide range of temperatures and stiffnesses without cracking or pull-away. Stabilizers containing emulsifiers, such as distilled monoglycerides, also impart creaminess and improved mouth release to peanut butter. Stabilizers should be added to the grinder when temperatures exceed their melting point. As the peanut butter cools, the stabilizer begins to crystallize, forming the matrix. For good stability, it is important that the peanut butter be packaged at the proper temperature. The peanut butter should be tempered for a minimum of 24 hours before shipping. This allows time for additional crystal growth and formation of a good crystalline network. Stabilizers are normally prepared from fully hydrogenated vegetable oils and/or distilled monoglycerides derived from fully hydrogenated vegetable oils. Mono- and diglycerides derived from fully hydrogenated vegetable oils are also used . . . The type and amount of stabilizer will depend on the desired consistency and mouth feel of the peanut butter along with the amount of oil present, particle size after grinding, and plant operating conditions.
The Eastman brochure suggests usage levels for these stabilizers in the range of 1.3% to 2.0% to solidify peanut butter.
Other manufacturers offer stabilizers with fully hydrogenated vegetable oils in combination with partially hydrogenated monoglycerides. The latter are reported to provide an agreeable creamy mouth feel. All of the peanut butter stabilizers containing fully hydrogenated and partially hydrogenated vegetable oils, are enriched in saturated fats and, being solid or semi-solid at room temperature, form a weak crystalline matrix when highly diluted (approximately 50-fold) into peanut butter. This semi-solid matrix prevents peanut oil separation.
Several significant limitations exist in the use of the currently marketed peanut butter stabilizers. For example, the stabilizers must be used with carefully controlled temperatures to control the fat crystallization and peanut butter "setting" process in order to achieve the proper peanut butter consistency and texture. Moreover, the elevated melting temperatures of the peanut butter stabilizers described above (which principally contain hydrogenated oils and/or monoglycerides with melting points between 63.degree. C. and 68.degree. C.) contrast with the much lower mouth temperature of 37.degree. C. These elevated melting temperatures contribute to the unpleasant sticky and fatty mouth feel of commercial peanut butter.
Furthermore, the stabilizers which contain partially hydrogenated fatty acids, contribute trans fatty acids such as elaidic acid to the diet. These trans fatty acids have been implicated in elevating serum cholesterol levels in humans and contributing to coronary heart disease. Accordingly, it would be desirable to find another edible agent with a more agreeable mouth feel which could replace some or all of the conventional stabilizers currently used in commercial peanut butters to prevent oil separation. Preferably, the stabilizer(s) would not be based on saturated or hydrogenated fats so that the health quality of peanut and other vegetable kernel butters could be improved. It would also be desirable if such an agent were already generally recognized as safe under the FDA or FDA-approved as a food ingredient or food additive.